Radio communication apparatus and pilot symbol transmission method

ABSTRACT

A radio communication apparatus is disclosed that enables the influence of the feedback information on the channel capacity to be kept to the minimum without reducing the transmission efficiency of information by transmission of pilot symbol. In the apparatus, a delay dispersion measuring section ( 272 ) generates a delay profile using the received signal, and measures delay dispersion indicative of dispersion of delayed versions. A moving speed estimating section ( 274 ) estimates moving speed of a mobile station apparatus that transmits a pilot symbol based on the variation in reception power of the pilot symbol. An other-cell interference measuring section ( 276 ) measures other-cell interference caused by signals transmitted in cells except the cell to which the apparatus belongs. Corresponding to the delay dispersion, moving speed and other-cell interference, a pilot pattern information generating section ( 278 ) selects a pilot pattern such that placement of pilot symbol is optimal in a frame, and generates the pilot pattern information.

TECHNICAL FIELD

The present invention relates to a radio communication apparatus andpilot symbol transmission method, and more particularly, to a radiocommunication apparatus and pilot symbol transmission method used in aradio communication system in which an individual pilot symbol istransmitted to each user.

BACKGROUND ART

In a radio communication system, since the propagation environmentvaries every instant, it is necessary for a signal receiving side tocompensate a received signal for the influence of the propagationenvironment. Therefore, the signal transmitted in the radiocommunication system generally contains a known pilot symbol. The signalreceiving side detects the state of distortion of the pilot symbol bychannel estimation, and, using the result, compensates data symbolsincluding information for the influence of the propagation environment.

Specifically, for example, as shown in FIG. 1, the signal transmittingside places a pilot symbol (diagonally shaded areas in the figure) atthe beginning of a frame, and data symbols (white areas in the figure)subsequent to the pilot symbol. Then, the receiving side performschannel estimation using the pilot symbols of two consecutive frames,performs interpolation, for example, and thereby compensates the datasymbols over these two pilot symbols for the propagation path variation.

Data symbols are thus compensated for the propagation path variationbased on channel estimation results of the pilot symbols arranged tosandwich the data symbols. Therefore, when the interval between pilotsymbols is decreased, the accuracy (the propagation path compensation ofthe data symbol) improves. In other words, when the proportion of pilotsymbols (in a frame) is increased, data symbols are received with higheraccuracy.

However, since the pilot symbol does not include information to betransmitted, when the proportion of pilot symbols (in a frame) isincreased, the proportion of data symbols is decreased and theinformation transmission efficiency is reduced.

In view of the foregoing, for example, Patent Document 1 discloses atechnique for adaptively determining the subcarrier in which a pilotsymbol is inserted according reception power differences betweensubcarriers with different frequencies in OFDM (Orthogonal FrequencyDivision Multiplexing). In the technique disclosed in Patent Document 1,(the signal receiving side) determines a subcarrier to insert a pilotsymbol, and transmits information on the subcarrier to a signaltransmitting side as feedback. Then, according to this feedbackinformation, the signal transmitting side inserts the pilot symbol totransmit.

Patent Document 1: JP 2003-174426

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

However, in the aforementioned technique, the signal receiving sideneeds to transmit information on the subcarrier to insert a pilot symbolas feedback every time, and there is a problem that the signal amountfor feedback becomes enormous. As a result, the feedback information mayconstrict the channel capacity.

In particular, when the inserting position of a pilot symbol isdetermined adaptively, since it is preferable that a common pilot symbolis transmitted from a base station apparatus to mobile stationapparatuses, determined mainly is the inserting position of a pilotsymbol on the uplink channel from the mobile station apparatus to basestation apparatus. Therefore, the feedback information is transmitted onthe downlink channel from the base station apparatus to mobile stationapparatuses. Accordingly, when the feedback information becomes enormousas in the above-mentioned technique, the channel capacity is constrictedon the downlink channel to transmit data with relatively a large amountof data amount such as moving picture and music distribution, and thecommunication quality may deteriorate.

It is therefore an object of the present invention to provide a radiocommunication apparatus and pilot symbol transmission method capable ofkeeping the influence of the feedback information to the channelcapacity to a minimum without reducing the transmission efficiency ofinformation by transmitting of pilot symbols.

Means for Solving the Problem

A radio communication apparatus of the invention adopts a configurationhaving: an acquirer that acquires a parameter comprising an indicator ofa propagation environment in which pilot symbols are transmitted; apilot pattern selector that selects a pilot pattern indicating positionsof the pilot symbols in a frequency domain and a time domain accordingto the parameter acquired; and a transmitter that transmits a signalincluding information of the pilot pattern selected. In other words,with the present invention, the pattern (hereinafter, referred to as a“pilot pattern”) of arranging pilot symbols is determined based onparameters indicating the propagation environment, and the pilot symbolsare transmitted according to pilot patterns.

Advantageous Effect of the Invention

According to the invention, the transmission efficiency of informationis not reduced by transmission of pilot symbol, and the influence of thefeedback information on the channel capacity can be kept to a minimum.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing an example of a conventional frame format;

FIG. 2 is a block diagram illustrating a configuration of principal partof a base station apparatus according to Embodiment 1;

FIG. 3 is a block diagram illustrating an internal configuration of apilot pattern selecting section according to Embodiment 1;

FIG. 4 is a block diagram illustrating a configuration of principal partof a mobile station apparatus according to Embodiment 1;

FIG. 5A is a view to explain a difference in the pilot pattern due toother-cell interference according to Embodiment 1;

FIG. 5B is another view to explain a difference in the pilot pattern dueto other-cell interference according to Embodiment 1;

FIG. 6A is a chart showing an example of a reception power variation inthe frequency domain according to Embodiment 1;

FIG. 6B is a chart showing another example of the reception powervariation in the frequency domain according to Embodiment 1;

FIG. 7A is a chart showing an example of the reception power variationin the time domain according to Embodiment 1;

FIG. 7B is a chart showing another example of the reception powervariation in the time domain according to Embodiment 1;

FIG. 8 is a view showing an example of pilot patterns corresponding todelay dispersion and moving speed according to Embodiment 1;

FIG. 9 is a block diagram illustrating a configuration of principal partof a base station apparatus according to Embodiment 2;

FIG. 10 is a block diagram illustrating a configuration of principalpart of a mobile station apparatus according to Embodiment 2;

FIG. 11 is a block diagram illustrating an internal configuration of apilot pattern selecting section according to Embodiment 2;

FIG. 12 is a block diagram illustrating an internal configuration of apilot pattern selecting section according to Embodiment 2;

FIG. 13 is a view showing an example of pilot patterns corresponding tomodulation schemes according to Embodiment 2;

FIG. 14 is a block diagram illustrating a configuration of principalpart of a base station apparatus according to Embodiment 3;

FIG. 15 is a block diagram illustrating an internal configuration of apilot pattern selecting section according to Embodiment 3;

FIG. 16 is a block diagram illustrating a configuration of principalpart of a mobile station apparatus according to Embodiment 3; and

FIG. 17 is a view showing an example of the correspondence relationshipbetween a pilot pattern and time slot according to Embodiment 3.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1

Embodiment 1 of the invention will specifically be described below withreference to the accompanying drawings. In the following descriptions, abase station apparatus and mobile station apparatus are assumed toperform communications in an OFDM (Orthogonal Frequency DivisionMultiplexing) system, and transmission of the pilot symbol on the uplinkchannel from the mobile station apparatus to base station apparatus willbe described.

FIG. 2 is a block diagram illustrating a configuration of principal partof a base station apparatus according to Embodiment 1 of the invention.The base station apparatus shown in the figure has a transmissionsection comprised of coding section 100, modulation section 110, codingsection 120, modulation section 130, subcarrier assigning section 140,IFFT (Inverse Fast Fourier Transform) section 150, GI (Guard Interval)inserting section 160 and radio transmission section 170, and areception section comprised of radio reception section 200, GI removingsection 210, FFT (Fast Fourier Transform) section 220, pilot extractingsection 230, channel estimation section 240, demodulation section 250,decoding section 260 and pilot pattern selecting section 270.

Coding section 100 encodes transmission data, and outputs coded data tomodulation section 110.

Modulation section 110 modulates the coded data output from codingsection 100, and outputs modulated data to subcarrier assigning section140.

Coding section 120 encodes pilot pattern information (described later)generated in pilot pattern selecting section 270, and outputs coded datato modulation section 130.

Modulation section 130 modulates the coded data output from codingsection 120, and outputs modulated data to subcarrier assigning section140.

Subcarrier assigning section 140 assigns a plurality of subcarriershaving frequencies orthogonal to one another, to the transmission dataand pilot pattern information. More specifically, for example,subcarrier assigning section 140 performs S/P (Serial/Parallel)transform on the transmission data to obtain parallel data of aplurality of sequences, and assigns subcarriers to data of each sequenceand the pilot pattern information.

IFFT section 150 performs inverse fast Fourier transform on thetransmission data and pilot pattern information and multiplex theresults on the respectively assigned subcarriers, and thus generates anOFDM signal.

GI inserting section 160 copies an end portion of the OFDM signal to thebeginning and inserts a guard interval.

Radio transmission section 170 performs predetermined radio transmissionprocessing (such as D/A conversion and up-conversion) on the OFDM signalwith the guard interval inserted therein to transmit via an antenna.

Radio reception section 200 receives the signal via an antenna, andperforms predetermined radio reception processing (down-conversion andA/D conversion) on the received signal to output to GI removing section210 and pilot pattern selecting section 270.

GI removing section 210 removes the guard interval from the receivedsignal, and outputs the OFDM signal from which the guard interval isremoved, to FFT section 220.

FFT section 220 performs fast Fourier transform on the OFDM signal, anddemultiplexes the data multiplexed on each subcarrier to output to pilotextracting section 230 and demodulation section 250.

Pilot extracting section 230 extracts a pilot symbol which is a knownsymbol, from data output from FFT section 220 according to the pilotpattern selected in pilot pattern selecting section 270 to output tochannel estimation section 240 and pilot pattern selecting section 270.

Channel estimation section 240 performs channel estimation using theknown pilot symbol, and outputs a result of the channel estimation todemodulation section 250.

Demodulation section 250 demodulates the data multiplexed on eachsubcarrier using the result of the channel estimation, and outputsdemodulated data to decoding section 260.

Decoding section 260 decodes the demodulated data, and outputs receptiondata.

Pilot pattern selecting section 270 selects a pilot pattern such thatthe arrangement of pilot symbols is optimal in the frequency domain andtime domain in a frame, corresponding to the propagation environmentbetween the base station apparatus and a mobile station apparatus as atransmission source of the pilot symbol. More specifically, as shown inFIG. 3, pilot pattern selecting section 270 has delay dispersionmeasuring section 272, moving speed estimating section 274, other-cellinterference measuring section 276 and pilot pattern informationgenerating section 278.

Delay dispersion measuring section 272 generates a delay profile usingthe received signal, and measures delay dispersion indicative ofdispersion of delayed waves. When the delay dispersion is large, i.e.the time is long between reception of a direct signal and reception ofall delayed waves, the frequency selective fading is great. Meanwhile,when the delay dispersion is small, the frequency selective fading isalso small. More specifically, for example, in the case of a propagationenvironment where delayed waves do not occur and only a direct signal istransmitted, the frequency selective fading does not exist.

In addition, in this Embodiment, it is described that a base stationapparatus generates a delay profile, but since signals are transmittedvia the same paths on the uplink and downlink channels in multipathpropagation paths, a mobile station apparatus may generate a delayprofile of the downlink channel to notify the base station, whilemeasuring the delay dispersion.

Moving speed estimating section 274 estimates the moving speed of amobile station apparatus that transmits a pilot symbol based on thevariation in reception power of the pilot symbol. In other words, movingspeed estimating section 274 estimates that the mobile station apparatusmoves at high speed when the variation is fast in reception power of thepilot symbol, while estimating that the mobile station apparatus stopsor moves at low speed when the reception power of the pilot symbol doesnot vary largely.

Using the pilot symbol, other-cell interference measuring section 276measures interference (other-cell interference) by signals transmittedin other cells than the cell to which the base station apparatusbelongs. Since the pilot symbol is known, other-cell interferencemeasuring section 276 is capable of measuring interference (i.e.other-cell interference) provided from signals of other cells on thepropagation path.

According to the delay dispersion, moving speed and other-cellinterference, pilot pattern information generating section 278 selectsthe pilot pattern such that the arrangement of pilot symbol in a frameis optimal, and generates pilot pattern information indicative of theselected pilot pattern. Selection of the pilot pattern will specificallybe described later.

FIG. 4 is a block diagram illustrating a configuration of principal partof a mobile station apparatus according to Embodiment 1 of theinvention. The mobile station apparatus as shown in the figure has areception section comprised of radio reception section 300, GI removingsection 310, FFT section 320, pilot extracting section 330, channelestimation section 340, demodulation section 350 and decoding section360, and a transmission section comprised of coding section 400,modulation section 410, pilot generating section 420, multiplexingsection 430, IFFT section 440, GI inserting section 450 and radiotransmission section 460.

Radio reception section 300 receives the signal via an antenna, andperforms predetermined radio reception processing (such asdown-conversion and A/D conversion) on the received signal to output toGI removing section 310.

GI removing section 310 removes the guard interval from the receivedsignal, and outputs the OFDM signal from which the guard interval isremoved to FFT section 320.

FFT section 320 performs fast Fourier transform on the OFDM signal, anddemultiplexes the data multiplexed on each subcarrier to output to pilotextracting section 330 and demodulation section 350.

Pilot extracting section 330 extracts a pilot symbol from the dataoutput from FFT section 320 to output to channel estimation section 340.

Channel estimation section 340 performs channel estimation using theknown pilot symbol, and outputs the channel estimation result todemodulation section 350.

Demodulation section 350 demodulates the data multiplexed on eachsubcarrier using the channel estimation result, and outputs demodulateddata to decoding section 360.

Decoding section 360 decodes the demodulated data to output receptiondata, while outputting the pilot pattern information in the demodulateddata to pilot generating section 420 and multiplexing section 430.

Coding section 400 encodes transmission data, and outputs coded data tomodulation section 410.

Modulation section 410 modulates the coded data output from codingsection 400, and outputs data symbols obtained to multiplexing section430.

Pilot generating section 420 generates pilot symbols of an amountaccording to the pilot pattern information to output to multiplexingsection 430.

According to the pilot pattern information, multiplexing section 430places a pilot symbol in a frame, multiplexes the pilot symbol and datasymbols, and transforms multiplexed data into parallel data to output toIFFT section 440.

IFFT section 440 performs inverse fast Fourier transform on the parallelmultiplexed data to multiplex on the respectively assigned subcarriers,and thus generates an OFDM signal.

GI inserting section 450 copies an end portion of the OFDM signal to thebeginning and inserts a guard interval.

Radio transmission section 460 performs predetermined radio transmissionprocessing (such as D/A conversion and up-conversion) on the OFDM signalwith the guard interval inserted therein to transmit via an antenna.

Described below is the operation of the base station apparatus andmobile station apparatus configured as described above using specificexamples.

Herein, first described is the operation of the base station apparatusfor a period during which radio reception section 200 in the basestation apparatus receives a signal, a pilot pattern is selected andpilot pattern information is transmitted.

A signal received from the antenna of the base station apparatus issubjected to predetermined radio reception processing (such asdown-conversion and A/D conversion), and output to GI removing section210 and delay dispersion measuring section 272 in pilot patternselecting section 270.

In the received signal, the guard interval is removed in GI removingsection 210, the resultant signal is subjected to fast Fourier transformin FFT section 220, and data multiplexed on each subcarrier is therebydemultiplexed and output to pilot extracting section 230 anddemodulation section 250.

Then, pilot extracting section 230 extracts a pilot symbol, and channelestimation section 240 performs channel estimation using the pilotsymbol. The channel estimation result is output to demodulation section250, and demodulation section 250 demodulates data using the channelestimation result. Then, demodulated data obtained by demodulation isdecoded in decoding section 260, and reception data is thereby obtained.

Further, the pilot symbol extracted by pilot symbol extracting section230 is output to moving speed estimating section 274 and other-cellinterference measuring section 276 in pilot pattern selecting section270.

Then, pilot pattern selecting section 270 selects an optimal pilotpattern as described below.

First, delay dispersion measuring section 272 generates a delay profileof the received signal to measure delay dispersion. As described above,the delay dispersion is an indicator of the level of frequency selectivefading. This Embodiment adopts the configuration where by the delaydispersion is measured by generating the delay profile, and anotherconfiguration may be used where by delay dispersion is in advance on aper cell basis. The delay dispersion is determined by, for example, theradius of the cell and the geographic features inside the cell, and isan almost constant value for each cell. Accordingly, such aconfiguration is available that stores the delay dispersion specific tothe cell that is measured in advance and obtained without calculatingthe delay dispersion by generating the delay profile. In such a case, itis possible to reduce the amount of calculation to select a pilotpattern and increase the speed of processing.

Further, moving speed estimating section 274 estimates the moving speedof a mobile station apparatus. In other words, the moving speed of amobile station apparatus is high when the variation in reception powerof the pilot symbol is high, while the moving speed of a mobile stationapparatus is low when the variation in reception power of the pilotsymbol is low.

Furthermore, other-cell interference measuring section 276 measuresother-cell interference provided from signals of other cells. Bycomparing the portion corresponding to the pilot symbol in the receivedsignal with the original pilot symbol, it is possible to measure theother-cell interference provided from signals of other cells on thepropagation path.

Based on parameters of delay dispersion, moving speed, and other-cellinterference, obtained as described above, pilot pattern informationgenerating section 278 selects a pilot pattern according to a policy asdescribed below, and generates pilot pattern information indicative ofthe selected pilot pattern.

When the other-cell interference measured in other-cell interferencemeasuring section 276 is large, since the reception quality degrades, itis required to increase the proportion of pilot symbols in a frame asshown in FIG. 5A to increase the reception quality. Meanwhile, when theother-cell interference is small, the proportion of pilot symbols in aframe is decreased as shown in FIG. 5B. In addition, in FIGS. 5A and 5B,diagonally shaded areas represent pilot symbols, while white areasrepresent data symbols. Further, each of FIGS. 5A and 5B shows oneframe, where the horizontal direction represents the level in the timedomain, and the vertical direction represents the level in the frequencydomain.

Further, when the delay dispersion measured in delay dispersionmeasuring section 272 is large, the frequency selectivity of fading islarge as shown in FIG. 6A, different fading is imposed on closefrequencies, and therefore, it is necessary to place pilot symbolsdensely in the frequency domain of a frame. Meanwhile, when the delaydispersion is small, the frequency selectivity of fading is small asshown in FIG. 6B, and it is not necessary to place pilot symbols denselyin the frequency domain of a frame.

Then, when the moving speed of the mobile station apparatus is highwhich is estimated in moving speed estimating section 274, the temporalvariation is intense in the propagation environment as shown in FIG. 7A,and it is thus necessary to place pilot symbols densely in the timedomain of a frame. Meanwhile, when the moving speed of the mobilestation apparatus is low, the temporal variation is moderate in thepropagation environment as shown in FIG. 7B, and it is not necessary toplace pilot symbols densely in the time domain of a frame.

In accordance with these policies, for example, according to theother-cell interference, pilot pattern information generating section278 first determines unit levels in the frequency domain and time domainof pilot symbol. In other words, when the other-cell interference islarge, for example, the unit level of pilot symbol is increased as shownin FIG. 5A (in the figure, each diagonally shaded rectangle representsone unit). Inversely, when the other-cell interference is small, theunit level of pilot symbol is decreased as shown in FIG. 5B, forexample.

Then, when the unit level of pilot symbol is determined, the arrangementof units is determined from the table shown in FIG. 8, for example, anda pilot pattern is selected. In addition, each pilot pattern shown inFIG. 8 indicates the arrangement of pilot symbol in a frame, and thediagonally shaded area represents the pilot symbol. Further, in eachpilot pattern, the horizontal direction represents the time domain,while the vertical direction represents the frequency domain.

In the example shown in FIG. 8, when the delay dispersion is less than apredetermined threshold Ta, only one unit of pilot symbol is arranged inthe frequency domain (patterns 1, 2 and 3). Then, when the delaydispersion is equal to or greater than the predetermined threshold Taand less than a predetermined threshold Tb, three units of pilot symbolsare arranged in the frequency domain (patterns 4, 5 and 6). Further,when the delay dispersion is equal to or greater than the predeterminedthreshold Tb, pilot symbols are arranged continuously in the frequencydomain (patterns 7 and 8).

Similarly, when the moving speed is less than a predetermined thresholdTc, only one unit of pilot symbol is arranged in the time domain(patterns 1, 4 and 7). Then, when the moving speed is the predeterminedthreshold Tc or more and less than a predetermined threshold Td, threeunits of pilot symbol are arranged in the time domain (patterns 2, 5 and8). Further, when the moving speed is equal to or greater than thepredetermined threshold Td, pilot symbols are arranged continuously inthe time domain (patterns 3 and 6).

In addition, in FIG. 8, when the delay dispersion is equal to or greaterthan the predetermined threshold Tb and the moving speed is thepredetermined threshold Td or more, the same pilot pattern (pattern 6 or8) is selected as the pattern when one of the delay dispersion andmoving speed is low. This is because the proportion of data symbols in aframe greatly decreases and the transmission efficiency of informationdegrades when pilot symbols are consecutive both in the frequency domainand time domain.

Actually, the fading variation over time is moderate as compared to thevariation in frequency selective fading, and therefore, when the delaydispersion and moving speed are both high, the pilot pattern (pattern 8)is selected where the delay dispersion is equal to or greater than thepredetermined threshold Tb and the moving speed is equal to or greaterthan the predetermined threshold Tc and less than the threshold Td.

To notify the mobile station apparatus of the pilot pattern selectedthus, pilot pattern information generating section 278 generates thepilot pattern information. Herein, in the above-mentioned example, sincetwo unit levels (FIGS. 5A and 5B) of pilot symbol exist that aredetermined according to the other-cell interference and eight patterns(FIG. 8) exist on each of the unit levels of pilot symbol, such pilotpattern information is generated that indicates which pilot pattern isselected from among sixteen (16=2×8) pilot patterns. Therefore, thepilot pattern information can be represented by maximum four bits(2⁴=16), and it is possible to prevent the channel capacity from beinginhibited by the feedback information to adaptively control transmissionof the pilot symbol. In addition, the above-mentioned pilot patterns areonly of one example, and it is possible to further reduce theinformation amount of the pilot pattern information depending on thenumber of pilot patterns.

The generated pilot pattern information is coded in coding section 120,modulated in modulation section 130, and output to subcarrier assigningsection 140. Further, the pilot pattern information is output to pilotextracting section 230. Pilot extracting section 230 extracts pilotsymbols that the mobile station apparatus transmits according to thepilot pattern information notified from the base station apparatus,according to the input pilot pattern information.

Meanwhile, transmission data is coded in coding section 100, modulatedin modulation section 110, and output to subcarrier assigning section140.

Then, subcarrier assigning section 140 assigns a subcarrier to each ofthe pilot pattern information and transmission data, IFFT section 150performs inverse fast Fourier transform, and an OFDM signal is generatedthat includes the pilot pattern information and transmission data.

Subsequently, GI inserting section 160 copies an end portion of the OFDMsignal to the beginning, thereby inserting a guard interval into theOFDM signal, radio transmission section 170 performs the predeterminedradio transmission processing (such as D/A conversion and up-conversion)on the signal, and the radio signal is transmitted through the antenna.

Described below is the operation of the mobile station apparatus for aperiod during which radio reception section 300 in the mobile stationapparatus receives the pilot pattern information and a signal includingpilot symbols is transmitted.

Radio reception section 300 performs the predetermined radio receptionprocessing (such as down-conversion and A/D conversion) on a signalreceived from the antenna of the mobile station apparatus. GI removingsection 310 removes the guard interval from the signal. FFT section 320performs fast Fourier transform on the signal, and demultiplexes thedata multiplexed on each subcarrier to output to pilot extractingsection 330 and demodulation section 350.

Then, pilot extracting section 330 extracts the pilot symbol. Channelestimation section 340 performs channel estimation using the pilotsymbol, and outputs the channel estimation result to demodulationsection 350. Demodulation section 350 demodulates the data using thechannel estimation result. Decoding section 360 decodes the demodulateddata obtained by demodulation, and obtains reception data and the pilotpattern information.

The obtained pilot pattern information is output to pilot generatingsection 420 and multiplexing section 430. Then, pilot generating section420 generates a number of pilot symbols enabling the frame configurationof the pilot pattern indicated by the pilot pattern information, andoutputs generated pilot symbols to multiplexing section 430.

Meanwhile, coding section 400 encodes transmission data, and modulationsection 410 modulates the data and outputs as data symbols tomultiplexing section 430.

According to the pilot pattern information, multiplexing section 430multiplexes the pilot symbols and data symbols, and generates a frame ofthe pilot pattern indicated by the pilot pattern information.

IFFT section 440 performs inverse fast Fourier transform on thegenerated frame, and thus generates an OFDM signal including the pilotsymbols and data symbols.

GI inserting section 450 copies an end portion of the OFDM signal to thebeginning and inserts a guard interval into the OFDM signal. Radiotransmission section 460 performs the predetermined radio transmissionprocessing (such as D/A conversion and up-conversion) on the signal, andthe radio signal is transmitted via the antenna.

Thereafter, the base station apparatus selects again a pilot pattern,and the aforementioned operation is repeated.

Thus, according to this Embodiment, a pilot pattern is selected totransmit pilot symbols that are optimal, necessary and sufficient forthe propagation environment using as parameters delay dispersion, movingspeed of the mobile station apparatus and interference caused by signalsof other cells. The transmission efficiency of information is therebynot reduced by transmission of pilot symbols, and it is possible to keepthe influence of feedback information on channel capacity to a minimum.

In addition, although a case has been described with this embodimentwhere pilot symbols are transmitted on the uplink channel, the inventionis not limited to this. A mobile station apparatus selects a pilotpattern, and notifies the base station apparatus of the pilot patterninformation, so that it is possible to control the transmission of pilotsymbols on the downlink channel from the base station apparatus to themobile station apparatus.

Further, although a case has been described with this embodiment wherecommunications is performed in the OFDM system, the invention is notlimited to this. The invention is applicable to multicarriercommunications other than the OFDM system, and communications using aCDMA (Code Division Multiple Access) system, TDMA (Time DivisionMultiple Access) system or the like.

Moreover, depending on the applied communication system, the proportionof pilot symbols in a frame is determined using as parameters allinterference amounts including interference by other mobile stationapparatuses in the cell and interference by multipath, as well as theother-cell interference.

Further, although a case has been described with this embodiment where aconfiguration is provided that selects a pilot pattern using threeparameters of delay dispersion, moving speed of a mobile stationapparatus and interference by signals of other cells at the same time,the invention is not limited to this, and a pilot pattern may beselected using only one or two of these parameters.

Furthermore, the parameters are not limited to above three parameters,and corresponding to any parameters that reflect the propagationenvironment, it is possible to determine an arrangement of pilot symbolsin the frequency domain and time domain of a frame.

Embodiment 2

The influence of the accuracy of channel estimation using the pilotsymbol on the bit error rate varies between modulation schemes. In otherwords, as the modulation scheme has a larger modulation level, higheraccuracy is required in channel estimation. Particularly, in QAMmodulation such as 16QAM and 64QAM, since judgment on amplitude isrequired as well as judgment on phase upon demodulation, high accuracyis required in channel estimation. Further, to achieve high accuracy inchannel estimation, it is necessary to increase a proportion of pilotsymbols (i.e. density of pilot symbols) in a frame.

Therefore, in this Embodiment, a pilot pattern is selected furtherconsidering the modulation scheme in addition to three parameters (delaydispersion, moving speed of a mobile station apparatus and other-cellinterference) used in Embodiment 1. In addition, in followingdescriptions, as in Embodiment 1, a base station apparatus and mobilestation apparatus are assumed to perform communications in the OFDMsystem, and described is transmission of the pilot symbol on the uplinkchannel from the mobile station apparatus to base station apparatus.

FIG. 9 is a block diagram illustrating a configuration of principal partof a base station apparatus according to Embodiment 2 of the invention.In addition to the configuration of Embodiment 1 (FIG. 2), the basestation apparatus according to this Embodiment has reception qualitymeasuring section 280 and MCS (Modulation and Coding Scheme) selectingsection 290.

Reception quality measuring section 280 measures the SIR as receptionquality using pilot symbols input from pilot extracting section 230, andoutputs a measurement value to MCS selecting section 290.

Based on the SIR value input from reception quality measuring section280, MCS selecting section 290 selects a modulation scheme and codingrate of data for the mobile station apparatus to transmit, and outputsinformation (MCS information) indicative of the selected modulationscheme and coding rate to pilot pattern selecting section 270 and codingsection 120. MCS selecting section 290 has a table (MCS table) set for aplurality of combinations of modulation scheme and coding rate enablingreception of data with a predetermined error rate respectively inrelation to a plurality of SIR values, and by referring to the MCS tablebased on the SIR value, selects the optimal combination of modulationscheme and coding rate from among the plurality of combinations. The MCSinformation is subjected to the same processing as in the pilot patterninformation and transmitted to the mobile station apparatus.

Pilot pattern selecting section 270 selects a pilot pattern furtherconsidering the modulation scheme selected in MCS selecting section 290in addition to the three parameters (delay dispersion, moving speed of amobile station apparatus and other-cell interference) described inEmbodiment 1. The selection method will be described later.

FIG. 10 is a block diagram illustrating a configuration of principalpart of a mobile station apparatus according to Embodiment 2 of theinvention. The configuration of the mobile station apparatus accordingto this Embodiment is the same as in Embodiment 1 (FIG. 4) except thatthe MCS information decoded in decoding section 360 is output to codingsection 400 and modulation section 410, and that the coding rate incoding section 400 and the modulation rate in modulation section 410 arecontrolled according to the MCS information. In other words, the mobilestation apparatus encodes data to transmit to the base station with thecoding rate indicated by the MCS information and modulates the data withthe modulation scheme indicated by the MCS information.

Described next is selection of pilot pattern in this Embodiment. Thereare two methods of selecting a pilot pattern in consideration of themodulation scheme. These are: a method (hereinafter, referred to asselection method 1) of selecting a pilot pattern according to FIG. 8using values obtained by adding an offset determined based on themodulation scheme to a measurement value of delay dispersion and anestimation value of moving speed, and another method (hereinafter,referred to as selection method 2) of inserting a number of pilotsymbols determined based on the modulation scheme between units of pilotsymbol in the pilot pattern determined according to FIG. 8.

<Selection Method 1>

In the case of selection method 1, the configuration of pilot patternselecting section 270 is as shown in FIG. 11. Pilot pattern selectingsection 270 as shown in FIG. 11 is configured with the configuration inEmbodiment 1 (FIG. 3) and further with offset adding section 271.

Offset adding section 271 receives the MCS information from MCSselecting section 290. Offset adding section 271 adds an offsetaccording to the modulation scheme indicated by the MCS information tothe delay dispersion input from delay dispersion measuring section 272and to the moving speed input from moving speed estimating section 274.The offset has a lager value as the modulation level is larger. In otherwords, the offset for 64QAM is larger than the offset for 16QAM, and theoffset for 16QAM is larger than the offset for QPSK. In addition, theoffset for QPSK can be set at zero. Further, it is possible to usedifferent values for the offset to add to the moving speed and theoffset to add to the delay dispersion. The delay dispersion and movingspeed with the offset added thereto are output to pilot patterninformation generating section 278.

Based on the delay dispersion and moving speed with the offset addedthereto, pilot pattern information generating section 278 makes adetermination with thresholds as described in Embodiment 1 (FIG. 8) andselects a pilot pattern. Since the offset is larger as the modulationlevel is larger, when the pilot pattern is thus selected, the proportionof pilot symbols in a frame, i.e. density of pilot symbols increases asthe modulation level is larger.

<Selection Method 2>

In the case of selection method 2, the configuration of pilot patternselecting section 270 is as shown in FIG. 12. Pilot pattern selectingsection 270 as shown in FIG. 12 is configured with the configuration inEmbodiment 1 (FIG. 3) and further with insertion pilot determiningsection 273.

Insertion pilot determining section 273 receives the MCS informationfrom MCS selecting section 290. Based on the modulation scheme indicatedby the MCS information, insertion pilot determining section 273determines the number of pilot symbols to insert between units of pilotsymbol. The number increases as the modulation level is larger. In otherwords, the number for 64QAM is larger than the number for 16QAM, and thenumber for 16QAM is larger than the number for QPSK. The determinednumber is output to pilot pattern information generating section 278.

Pilot pattern information generating section 278 selects a pilot patternobtained by further inserting a number of pilot symbols determined ininsertion pilot determining section 273 to the pilot pattern selected asa result of the determination with thresholds as described in Embodiment1 (FIG. 8). For example, when the moving speed is Tc or more and lessthan Td and the delay dispersion is Ta or more and less than Tb, pattern5 in FIG. 8 is first selected. Then, for example, in the case thatinsertion numbers are determined beforehand such that the number forQPSK is zero, the number for 16QAM is one and the number for 64QAM istwo, pilot patterns selected for the modulation schemes are as shown inFIG. 13. In other words, in the case where the modulation scheme isQPSK, since the insertion number is zero, pattern 5 in FIG. 8 isselected without change. Further, in the case where the modulationscheme is 16QAM, since the insertion number is one, such a pattern isselected that one pilot symbol is further inserted between units ofpilot symbol in pattern 5 in FIG. 8. Furthermore, in the case where themodulation scheme is 64QAM, since the insertion number is two, such apattern is selected that two pilot symbols are further inserted betweenunits of pilot symbol in pattern 5 in FIG. 8. Since the number of pilotsymbols to insert is increased as the modulation level is larger, whenthe pilot pattern is thus selected, the proportion of pilot symbols in aframe (i.e. density of pilot symbols) increases as the modulation levelis larger.

In QAM modulation such as 16QAM and 64QAM, as described above, sincejudgment on amplitude is made as well as judgment on phase upondemodulation, the error rate is greatly improved by responding to atleast the amplitude variation. In other words, QAM modulation only needsminimum pilot symbols required to respond to the amplitude variation.Therefore, in selection method 2, as shown in FIG. 13, a unit of pilotsymbol to insert in the case where the modulation scheme is 16QAM and64QAM may be made smaller than a unit of pilot symbol in the pilotpattern (FIG. 8) selected based on the moving speed and delaydispersion. It is thus possible to prevent the data transmissionefficiency from deteriorating due to an increase in the proportion ofpilot symbols in a frame.

In addition, both in selection method 1 and selection method 2, as inEmbodiment 1, it is possible to control the proportion of pilot symbolsin a frame further using the other-cell interference.

Thus, according to this Embodiment, since the proportion of pilotsymbols in a frame is varied according to the modulation scheme, it ispossible to select a pilot pattern to transmit optimal, necessary andsufficient pilot symbols according to the modulation scheme.

Embodiment 3

Embodiments 1 and 2 describe transmission of pilot symbol on the uplinkchannel from the mobile station apparatus to the base station apparatus.This Embodiment describes transmission of pilot symbol on the downlinkchannel from the base station apparatus to the mobile station apparatus.Further, in this Embodiment, the base station apparatus and mobilestation apparatus are assumed to perform communications in the OFDMsystem as in Embodiments 1 and 2, and further, perform communicationsfor each time slot as a transmission unit basis.

FIG. 14 is a block diagram illustrating a configuration of principalpart of a base station apparatus according to Embodiment 3. In FIG. 14,the same structural elements as in Embodiment 1 (FIG. 2) are assignedthe same reference numerals to omit descriptions thereof.

Coding sections 100-1 to 100-K and modulation sections 110-1 to 110-Kperform coding and modulation on transmission data 1 to K to mobilestation apparatuses 1 to K, respectively. The modulated transmissiondata 1 to K is output to time slot assigning section 180.

Pattern information input to coding section 120 is information to notifythe mobile station apparatus of which pilot pattern is set for each timeslot constituting one frame. The pattern information is encoded incoding section 120, modulated in modulation section 130, and output totime slot assigning section 180.

As shown in FIG. 15, pilot pattern selecting section 270 is comprised ofdelay dispersion measuring section 272, moving speed estimating section274, and pilot pattern information generating section 278, and based onthe delay dispersion and moving speed of each mobile station apparatus,selects a pilot pattern of pilot symbol to transmit on the downlinkchannel for each mobile station apparatus. The selection method will bedescribed later. The pilot pattern information generated in pilotpattern information generating section 278 is output to time slotassigning section 180.

Time slot assigning section 180 determines which time slot in a frame isassigned transmission data for which mobile station apparatus, accordingto the pilot pattern for each mobile station apparatus selected in pilotpattern selecting section 270. The assignment method will be describedlater. Then, time slot assigning section 180 inputs assignmentinformation indicative of which time slot is assigned transmission datato which mobile station apparatus to coding section 120. The assignmentinformation is encoded in coding section 120, modulated in modulationsection 130, and input to time slot assigning section 180. Time slotassigning section 180 assigns transmission data 1 to K respectively tomobile station apparatuses 1 to K, pattern information and assignmentinformation to each time slot in a frame, and outputs each time slotassigned such data and information to multiplexing section 190successively.

Multiplexing section 190 multiplexes transmission data 1 to K, patterninformation, assignment information and pilot symbols according to thepilot pattern on a per timeslot basis. Each multiplexed time slot issubjected to inverse fast Fourier transform in IFFT section 150.

FIG. 16 is a block diagram illustrating a configuration of principalpart of a mobile station apparatus according to Embodiment 3 of theinvention. The configuration of the mobile station apparatus accordingto this Embodiment is the same as in Embodiment 1 (FIG. 4) except thatthe pilot pattern information decoded in decoding section 360 is inputto pilot extracting section 330, and that according to the input pilotpattern information, pilot extracting section 330 extracts pilot symbolsfrom data output from FFT section 320.

Described next is selection of pilot pattern and assignment of time slotin this Embodiment. In addition, it is assumed in the followingdescriptions that one frame is comprised of eight time slots (TS1 toTS8), and that assignment to each time slot is performed for each frame.In addition, the number of time slots constituting one frame is notlimited to eight.

As shown in FIG. 17, each time slot (TS1 to TS8) constituting one frameis set for a pilot pattern as shown in FIG. 8. In addition, here, thepilot pattern shown in FIG. 8 represents the arrangement of pilotsymbols in each time slot. The pattern information is information toindicate which pilot pattern among pilot patterns 1 to 8 is set on eachtime slot of TS1 to TS8. In addition, the pilot pattern for each timeslot may be set beforehand and fixed, or varied for each frame accordingto the number of mobile station apparatuses for which the pilot patternis selected, the channel quality and the like. Further, the same pilotpattern may be set on a plurality of time slots.

In pilot pattern selecting section 270, for each mobile stationapparatus, delay dispersion measuring section 272 measures the delaydispersion, and moving speed estimating section 274 estimates the movingspeed. In this Embodiment, since data transmission from each mobilestation apparatus on the uplink channel is also performed in timedivision on a per timeslot basis, pilot pattern selecting section 270 iscapable of measuring the delay dispersion and moving speed for eachmobile station apparatus. Based on the delay dispersion and movingspeed, pilot pattern information generating section 278 makes adetermination with thresholds described in Embodiment 1 (FIG. 8), andselects a pilot pattern for each mobile station apparatus. At thispoint, pilot pattern information generating section 278 selects a pilotpattern for each mobile station apparatus from pilot patterns other thanpattern 8. As described above, pattern 8 has the best response to thevariation in propagation environment among patterns 1 to 8, andtherefore is set on TS1 that is a time slot in the beginning of a frame,while being fixed to be used as a pilot pattern of the patterninformation and assignment information. In addition, when the delaydispersion is the predetermined threshold Tb or more and the movingspeed is equal to or greater than the predetermined threshold Tc in FIG.8, pilot pattern information generating section 278 is assumed to selectpattern 6 instead of pattern 8. It is assumed in the followingdescriptions that five mobile station apparatuses 1 to 5 (MS1 to 5)exist, pattern 6 is selected for mobile station apparatuses 1 and 2 (MS1and MS2), pattern 5 is selected for mobile station apparatuses 3 and 4(MS3 and MS4), and that pattern 3 is selected for mobile stationapparatus 5 (MS5). It is thus possible to select one pilot pattern for aplurality of mobile station apparatuses at the same time, so that theplurality of mobile station apparatuses are able to share one pilotpattern. Then, the pilot pattern information indicative of the selectionresult is input to time slot assigning section 180.

According to the pilot pattern selected for each mobile stationapparatus in pilot pattern selecting section 270, time slot assigningsection 180 assigns transmission data for each mobile station apparatusto each time slot. In other words, transmission data 1 for mobilestation apparatus 1 for which pattern 6 is selected is assigned to TS3on which pattern 6 is set. At the same time, transmission data 2 formobile station apparatus 2 for which pattern 6 is selected is assignedto TS3, transmission data 3 and 4 for mobile station apparatuses 3 and 4for which pattern 5 is selected is assigned to TS4 on which pattern 5 isset, and transmission data 5 for mobile station apparatus 5 for whichpattern 3 is selected is assigned to TS6 on which pattern 3 is set.Thus, as a result of selecting one pilot pattern for a plurality ofmobile station apparatuses at the same time, transmission data to aplurality of mobile station apparatuses is assigned to one time slot.

Further, the assignment information indicative of a result of theassignment and pattern information are always assigned to TS1 that isthe first time slot on which pattern 8 is set. The assignmentinformation and pattern information need to be received by all mobilestation apparatuses in the cell, more important information than userdata, and therefore, requires use of the pilot pattern such thatsufficient pilot symbols are configured both in the frequency domain andtime domain. By receiving TS1, each mobile station apparatus is capableof knowing (in which time slot and in which pilot pattern) data for themobile station apparatus is transmitted.

According to one of pilot patterns 1 to 8 set on each time slot,multiplexing section 190 multiplexes transmission data and pilotsymbols. Further, when transmission data to a plurality of mobilestation apparatuses is assigned to one time slot, multiplexing section190 multiplexes a plurality of items of transmission data. Transmissiondata is multiplexed, for example, using the direct spreading scheme,frequency hopping scheme and the like. Accordingly, on TS3 ismultiplexed transmission data 1 for mobile station apparatus 1,transmission data 2 for mobile station apparatus 2 and pilot symbolsaccording to pattern 6. Likewise, on TS4 is multiplexed transmissiondata 3 for mobile station apparatus 3, transmission data 4 for mobilestation apparatus 4 and pilot symbols according to pattern 5, and on TS6is multiplexed transmission data 5 for mobile station apparatus 5 andpilot symbols according to pattern 3.

Thus, in this Embodiment, in transmission of pilot symbols on thedownlink channel, different pilot patterns are set per time slot, and,in according with pilot patterns selected according to the propagationenvironment of each mobile station apparatus, transmission data isassigned to each time slot. In this way, pilot symbols in the commonpilot pattern can be transmitted to a plurality of mobile stationapparatuses in the same propagation environment state, and it is thuspossible to improve the transmission efficiency on the downlink channel.

In addition, as well as mobile station apparatuses and base stationapparatuses, the invention is applicable to all radio communicationapparatuses used in radio communication systems where pilot symbols areused to estimate the propagation environment and the like.

Each of functional blocks used in the descriptions of each ofabove-mentioned Embodiments is implemented typically as an LSI which isan integrated circuit. These blocks may be configured in one-chip form,or one chip may include part or all of the blocks.

Herein, the LSI is assumed, but the circuit may be referred to as an IC,system LSI, super LSI, ultra LSI and so forth, depending on the degreeof integration.

Further, the method of integrating circuits is not limited to the LSI,and may be achieved by a dedicated circuit or general processor. It maybe possible to use FPGA (Field Programmable Gate Array) enablingprogramming after manufacturing the LSI, a reconfigurable processorenabling reconfiguration of connection or setting in the circuit cellinside the LSI, or the like.

Furthermore, if technique appears for integrating circuits substitutingfor the LSI with progress in semiconductor technique or another derivedtechnique, the functional blocks will naturally be integrated using suchtechnique. Adaptation and the like of biotechnology may have thepotential.

A first aspect of a radio communication apparatus of the inventionadopts a configuration having: an acquirer that acquires a parametercomprising an indicator of a propagation environment in which pilotsymbols are transmitted; a pilot pattern selector that selects a pilotpattern indicating positions of the pilot symbols in a frequency domainand a time domain according to the parameter acquired; and a transmitterthat transmits a signal including information of the pilot patternselected.

According to this configuration, since the pilot pattern in thefrequency domain and the time domain is selected according to theparameter as an indicator of the propagation environment and informationof the pilot pattern is transmitted, it is only required to notify acommunicating party of which pilot pattern is selected as feedback, andit is thus possible to prevent increases in information amount of thefeedback information. Concurrently, the communicating party is capableof transmitting an optimal pilot symbol corresponding to the propagationenvironment, and it is possible to keep the influence of the feedbackinformation on the channel capacity to a minimum without reducing thetransmission efficiency of information by transmission of pilot symbol.

A second aspect of the radio communication apparatus of the inventionadopts a configuration in which the acquirer has an interference amountmeasurer that measures an amount of interference caused by signalstransmitted from a radio communication apparatus other than acommunicating party or by multipath signals; and the pilot patternselector selects a pilot pattern whereby a proportion of the pilotsymbols is greater when the amount of interference increases.

According to this configuration, since a pilot pattern is selected suchthat the proportion of pilot symbols is larger in a frame when theamount of interference increases, it is possible to preventdeterioration in reception quality due to interference from other radiocommunication apparatuses and multipath interference, improve accuracyin channel estimation, and properly demodulate data symbols.

A third aspect of the radio communication apparatus of the inventionadopts a configuration in which the interference amount measurermeasures the amount of interference using the pilot symbols contained ina received signal.

According to this configuration, since the interference amount ismeasured using the pilot symbols contained in the received signal, it ispossible to measure the interference amount accurately by comparing witha known pilot symbol.

A fourth aspect of the radio communication apparatus of the inventionadopts a configuration in which the acquirer has a delay dispersionmeasurer that measures delay dispersion indicated by delayed waves of areceived signal; and the pilot pattern selector selects a pilot patternwhereby the pilot symbols are densely arranged in the frequency domainwhen the delay dispersion increases.

According to this configuration, since a pilot pattern is selected suchthat the pilot symbols are densely arranged in the frequency domain whenthe delay dispersion increases, even when the delay dispersion is largeand the variation is intense in frequency selective fading, it ispossible to improve the accuracy in channel estimation and properlydemodulate data symbols multiplexed on subcarriers with differentfrequencies, for example.

A fifth aspect of the radio communication apparatus of the inventionadopts a configuration in which the delay dispersion measurer generatesa delay profile of the received signal and measures the delaydispersion.

According to this configuration, since the delay profile of the receivedsignal is generated and the delay dispersion is measured, it is possibleto measure accurate delay dispersion every time a signal is received.

A sixth aspect of the radio communication apparatus of the inventionadopts a configuration where the delay dispersion measurer stores inadvance the delay dispersion corresponding to the shape of the cellwhere the apparatus belongs.

According to this configuration, since the delay dispersioncorresponding to the shape of the cell where the apparatus belongs isstored in advance, it is possible to reduce the amount of calculation tomeasure the delay dispersion and increase the speed of the processing.

A seventh aspect of the radio communication apparatus of the inventionadopts a configuration in which the acquirer has a moving speedestimator that estimates moving speed of the apparatus or acommunicating party, and the pilot pattern selector selects a pilotpattern that the pilot symbols are densely arranged in the time domainas the moving speed increases.

According to this configuration, since a pilot pattern is selected suchthat the pilot symbol is densely configured in the time domain as themoving speed is higher, even when the moving speed is high and thetemporal fading variation is intense, it is possible to improve theaccuracy of channel estimation and properly demodulate data symbols.

An eighth aspect of the radio communication apparatus of the inventionadopts a configuration in which the moving speed estimator estimates themoving speed based on a variation in reception power of the pilotsymbols contained in the received signal.

According to this configuration, since the moving speed is estimatedbased on the variation in reception power of the pilot symbols containedin the received signal, it is possible to estimate the moving speedaccurately with simple calculation.

A ninth aspect of the radio communication apparatus of the inventionadopts a configuration in which a modulation scheme selector is furtherprovided that selects a modulation scheme selector that selects amodulation scheme of data transmitted from a communicating party,wherein the pilot pattern selector selects the pilot patterncorresponding to the parameter and a modulation level of the modulationscheme selected in the modulation scheme selector.

A tenth aspect of the radio communication apparatus of the inventionadopts a configuration in which the pilot pattern selector selects apilot pattern whereby the pilot symbols are densely arranged in the timedomain or in the frequency domain as the modulation level of themodulation scheme selected in the modulation scheme selector increases.

An eleventh aspect of the radio communication apparatus of the inventionadopts a configuration in which an adder is further provided that addsto the parameter an offset with a value that varies with the modulationlevel of the modulation scheme selected in the modulation schemeselector, wherein the pilot pattern selector selects the pilot patternaccording to the parameter with the offset added thereto.

A twelfth aspect of the radio communication apparatus of the inventionadopts a configuration in which the pilot pattern selector selects apilot pattern obtained by further inserting a number of pilot symbols inaccordance with the modulation level of the modulation scheme selectedin the modulation scheme selector to the pilot pattern selectedaccording to the parameter.

According to these configurations, since the proportion of pilot symbolsvaries with the modulation scheme, it is possible to select a pilotpattern to transmit optimal, necessary and sufficient pilot symbolsaccording to the modulation scheme.

A thirteenth aspect of the radio communication apparatus of theinvention adopts a configuration in which: the transmitter transmits asignal containing pilot symbols arranged according to a pilot patternset per time slot; and the pilot pattern selector selects a pilotpattern for each of a plurality of communicating parties.

A fourteenth aspect of the radio communication apparatus of theinvention adopts a configuration in which an assigner is furtherprovided that assigns a time slot to each of the plurality ofcommunicating parties based on the pilot pattern selected in the pilotpattern selector.

According to these configurations, since a common pilot pattern of thepilot symbol can be transmitted to a plurality of communicating partiesin the same propagation environment state, it is possible to improvetransmission efficiency on the downlink channel.

A first aspect of a pilot symbol transmission method of the inventionhas the steps of acquiring a parameter comprising an indicator of apropagation environment in which pilot symbols are transmitted;selecting a pilot pattern indicating positions of the pilot symbols in afrequency domain and a time domain according to the parameter acquired;and transmitting a signal including information of the pilot patternselected.

According to this method, since the pilot pattern in the frequencydomain and the time domain is selected according to the parameter as anindicator of the propagation environment and information of the pilotpattern is transmitted, it is only required to notify a communicatingparty of which pilot pattern is selected as feedback, and it is thuspossible to prevent increases in information amount of the feedbackinformation. Concurrently, the communicating party is capable oftransmitting optimal pilot symbols corresponding to the propagationenvironment, and it is possible to keep the influence of the feedbackinformation on the channel capacity to a minimum without reducing thetransmission efficiency of information by transmission of pilot symbol.

This application is based on the Japanese Patent Applications No.2003-292667 filed on Aug. 12, 2003, and No. 2004-162388 filed on May 31,2004, entire contents of which are expressly incorporated by referenceherein.

INDUSTRIAL APPLICABILITY

The radio communication apparatus and pilot symbol transmission methodaccording to the invention enable the influence of the feedbackinformation on the channel capacity to be kept to the minimum withoutreducing the transmission efficiency of information by transmission ofpilot symbol, and are useful as a radio communication apparatus andpilot symbol transmission method used in a radio communication system inwhich an individual pilot symbol is transmitted for each user.

1. A radio communication apparatus comprising: an acquirer that acquiresa parameter comprising an indicator of a propagation environment inwhich pilot symbols are transmitted; a pilot pattern selector thatselects a pilot pattern indicating positions of the pilot symbols in afrequency domain and a time domain according to the parameter acquired;and a transmitter that transmits a signal including information of thepilot pattern selected.
 2. The radio communication apparatus accordingto claim 1, wherein: the acquirer has an interference amount measurerthat measures an amount of interference caused by signals transmittedfrom a radio communication apparatus other than a communicating party orby multipath signals; and the pilot pattern selector selects a pilotpattern whereby a proportion of the pilot symbols is greater when theamount of interference increases.
 3. The radio communication apparatusaccording to claim 2, wherein the interference amount measurer measuresthe amount of interference using the pilot symbols contained in areceived signal.
 4. The radio communication apparatus according to claim1, wherein: the acquirer has a delay dispersion measurer that measuresdelay dispersion indicated by delayed waves of a received signal; andthe pilot pattern selector selects a pilot pattern whereby the pilotsymbols are densely arranged in the frequency domain when the delaydispersion increases.
 5. The radio communication apparatus according toclaim 4, wherein the delay dispersion measurer generates a delay profileof the received signal and measure the delay dispersion.
 6. The radiocommunication apparatus according to claim 4, wherein the delaydispersion measurer stores in advance the delay dispersion correspondingto a shape of a cell to where the radio communication apparatus belongs.7. The radio communication apparatus according to claim 1, wherein theacquirer has a moving speed estimator that estimates moving speed of theapparatus or a communicating party, and the pilot pattern selectorselects a pilot pattern that the pilot symbol is densely configured inthe time domain as the moving speed increases.
 8. The radiocommunication apparatus according to claim 7, wherein the moving speedestimator estimates the moving speed based on a variation in receptionpower of the pilot symbols contained in the received signal.
 9. Theradio communication apparatus according to claim 1, further comprising:a modulation scheme selector that selects a modulation scheme of datatransmitted from a communicating party, wherein the pilot patternselector selects the pilot pattern corresponding to the parameter and amodulation level of the modulation scheme selected in the modulationscheme selector.
 10. The radio communication apparatus according toclaim 9, wherein the pilot pattern selector selects a pilot patternwhere the pilot symbols are densely arranged in the time domain or inthe frequency domain when the modulation level of the modulation schemeselected in the modulation scheme selector increases.
 11. The radiocommunication apparatus according to claim 9, further comprising: anadder that adds to the parameter an offset with a value that varies withthe modulation level of the modulation scheme selected in the modulationscheme selector, wherein the pilot pattern selector selects the pilotpattern according to the parameter with the offset added thereto. 12.The radio communication apparatus according to claim 9, wherein thepilot pattern selector selects a pilot pattern obtained by furtherinserting a number of pilot symbols in accordance with the modulationlevel of the modulation scheme selected in the modulation schemeselector to the pilot pattern selected according to the parameter. 13.The radio communication apparatus according to claim 1, wherein: thetransmitter transmits a signal containing pilot symbols arrangedaccording to a pilot pattern set per time slot; and the pilot patternselector selects a pilot pattern for each of a plurality ofcommunicating parties.
 14. The radio communication apparatus accordingto claim 13, further comprising an assigner that assigns a time slot toeach of the plurality of communicating parties based on the pilotpattern selected in the pilot pattern selector.
 15. A pilot symboltransmission method comprising: acquiring a parameter comprising anindicator of a propagation environment in which pilot symbols aretransmitted; selecting a pilot pattern indicating positions of the pilotsymbols in a frequency domain and a time domain according to theparameter acquired; and transmitting a signal including information ofthe pilot pattern selected.